Lower vs upper extremity injection of agitated saline for identification of patent foramen ovale (LOCATE)

Upper extremity injection of agitated saline using echocardiography is standard for locating patent foramen ovale (PFO), but several studies found the lower extremity to be more sensitive.

In this prospective study, patients were selected who had a prior embolic stroke of undetermined source by history and no PFO identified with transthoracic echocardiography. We placed intravenous access in the upper extremity and used ultrasound-guided access in the superficial greater saphenous vein in the lower extremity, evaluating best view and presence and size of PFO if found.

On review of 910 subjects, twenty subjects completed the study. The average greater saphenous vein measured 0.49 ± 0.16 cm in diameter, and depth of 1.07 ± 0.66 cm. The apical four chamber view to visualize the atrial septum was considered superior (p < 0.005) to the subcostal and parasternal short axis views. A PFO was found in five of the twenty subjects with concordance among all readers via lower extremity injection, compared to four subjects via upper extremity injection. Lower extremity injection of contrast identified significantly (p < 0.05) larger PFO compared to upper extremity injection. Complications from greater saphenous vein access included one superficial thrombus, one vasovagal syncope and four with ecchymosis (all < 3cm).

PFO are found significantly larger when utilizing the greater saphenous vein of the lower extremity compared to the upper extremity for injection of agitated saline and best visualized with the apical four-chamber view.